Rubble from segments of the Interstate 10 Twin Spans destroyed during Hurricane Katrina will be stuffed inside metal rebar “mattresses” that will be draped along a 7.8-mile stretch of the Lake Borgne shoreline to reduce erosion of the eastern New Orleans landbridge, Gov. Bobby Jindal and New Orleans Mayor Mitch Landrieu announced Wednesday.

The landbridge, a narrow mixture of hard land, wetlands and lakes that stretches across the Lake St. Catherine area towards Slidell and Mississippi, has been eroding at a rate of 8 feet per year.

“Without the landbridge, higher volumes of water would have been forced into Lake Pontchartrain and the effects of Hurricanes Katrina, Gustav and Ike would have been even worse than they already were,” Jindal said at a news conference in the Causeway Commission office in Metairie.

He said that the project adds to the new protection provided to New Orleans and St. Bernard parishes by the just-completed hurricane surge barrier across the Gulf Intracoastal Waterway and Mississippi River-Gulf Outlet.

“If we don’t save the coast, we’re toast,” said Carlton Dufrechou, executive director of the causeway commission and former executive director of the Lake Pontchartrain Basin Foundation. “Not only for New Orleans and East Jefferson, but for St. Tammany Parish, if that landbridge barrier goes, we all go.”

The project also protects the southern edge of the Bayou Sauvage Urban National Wildlife Refuge.

The $30.42 million mattress project being built by Bertucci Contracting Company, LLC, of New Orleans, is financed by the federal Coastal Impact Assistance Program, which uses offshore oil revenue to build restoration and infrastructure projects requested by states and localities in areas impacted by offshore oil and gas production in the Gulf of Mexico.

Included is $20.86 million in state CIAP money and $9.56 million in CIAP money awarded to the city of New Orleans.

Jindal said recycling concrete from the I-10 bridge, instead of buying concrete for the project, resulted in a $11.55 million savings for the project. Concrete from the bridge also is being used to build fishery reefs in Lake Pontchartrain, and a fishing pier in Slidell.

Rubble from 658 bridge spans and 586 substructures, representing 86,807 cubic yards of crushed concrete, will be used for the mattresses. The concrete crushing operation is being done by NASDI Inc.

Each mattress will be 38 feet long by 5 feet wide, and 18 inches thick. The first 16 feet of a mattress will lie along the highest ground along the shoreline, with the remainder draped into the adjacent water, with the bottom end buried and anchored in the lake bed to prevent movement.